The mechanical separation of constituents comprising a commingled material has been an ages old art. These separation actions have applied to food, such as separating wheat from chaff; or to minerals, such as separating gold from gold-bearing gravels. It has also applied to the separation of animal excrement from the animal's bedding. While in some areas there is an abundance of inexpensive bedding for animals wherein soiled bedding may be disposed of, for the most part, bedding is reused at least once by separating the feces there from.
The traditional means for carrying out such mechanical separation of feces from bedding has relied upon manual efforts in combination with a manure fork or other tined tool where the manure is thrown into a muck bucket or wheelbarrow. Standard manure forks for horse stalls have 18 tines, spaced about 0.75 inches apart, allowing manure particles smaller than about 0.75 inch to fall through with the used bedding. It has been estimated that approximately 20% of the manure is left behind. Newer forks with 30 tines spaced about 0.375 inches apart are an improvement, but by some measurements still allow about 15% of the manure to remain and increase the time and effort to conduct the required separation actions.
While generally effective, hand picking is tedious and time consuming. The average time to clean a horse stall is 15 to 20 minutes if done well. However, if one is required to clean many stalls over a long period of time, the manual method takes its toll on the body and can cause tennis elbow, carpal tunnel syndrome and chronic back pain. To minimize these deleterious consequences of hand picking, the cleaner will often throw good bedding away with the waste, or fail to remove all of the waste. In other words, time can be saved at the expense of bedding or bedding can be saved at the expense of time.
To address these deficiencies, power assisted mechanical separators have been developed and used. The general approach has been to emulate the process of manually mechanically separating the feces from the bedding. In this respect, these efforts have been generally successful. However, there continues to be constraints in the prior efforts of achieving a high efficiency power assisted mechanical separator, most notably the amount of kinetic energy imparted by the sifting surface to the bedding, as well as adaptability of such devices in light of changing environmental conditions such as relative humidity, temperature, and moisture content of the bedding, moisture content of the feces, binding of the feces, etc.